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Best Opamp for the Pimeta?

May 25, 2007 at 1:57 PM Post #16 of 27
I currently use an OPA2107 for the L/R and an LM6171 for the ground in the one I buit for my son (discrete buffers also). One that is really supposed to be good (I have them but haven't tried them yet) is the AD744 bypassing the on-chip buffers (output from pin 5 instead of 6).
 
May 26, 2007 at 9:01 AM Post #20 of 27
Quote:

Originally Posted by cocolaj /img/forum/go_quote.gif
I am using Dual 8610 on the stereo channel and single 8610 on the ground channel. Would switchen til 8620 on the stereo channel improve the sound consideredly?


No, it would probably worsen the sound. especially the crossover... two separated chips vs. one chip with two opamps very very close together
 
May 27, 2007 at 5:14 AM Post #21 of 27
Quote:

Originally Posted by balou /img/forum/go_quote.gif
No, it would probably worsen the sound. especially the crossover... two separated chips vs. one chip with two opamps very very close together


Does that hold true for all opamps in general?--that is, two single-channels adapted to a dual socket will give better performance than the same family dual-channel chip?
 
May 27, 2007 at 5:20 AM Post #22 of 27
Quote:

Originally Posted by cocolaj /img/forum/go_quote.gif
Do you know where to buy the OPA656 (or better yet the OPA655)?


656 is easy to get. Digikey and Newark both sell it. 655...I'm not sure...

I'd forgotten that the PIMETA uses a dual for L/R, though, so I guess you'd have to use an adaptor...which makes me wonder about how bypassing would work out. It's hard to find a good dual -_-

Also, are you using BUF634 for the buffer? If you are, then I guess the 8610/20 would work alright with that due to how the 634 tends to impact the signal.
 
May 27, 2007 at 8:08 AM Post #24 of 27
Quote:

Originally Posted by ChickenGod /img/forum/go_quote.gif
What about the AD8397?


I did plug'n'play with AD8397 in a Sijosae AB-amp (no fancy decoupling caps or ground plane). No problems whatsoever. I can't see why it shouldn't work in a PIMETA. It's a very "fun" opamp, like AD8620 with aural exciter. More slam than anything I've heard. It even makes the LM4562 sound dull, not to talk about OPA2107. Soundstage is at least on par with AD8620. But... it's very forward sounding and harsh.
 
May 27, 2007 at 9:11 AM Post #25 of 27
Quote:

Originally Posted by NelsonVandal /img/forum/go_quote.gif
I did plug'n'play with AD8397 in a Sijosae AB-amp (no fancy decoupling caps or ground plane). No problems whatsoever. I can't see why it shouldn't work in a PIMETA. It's a very "fun" opamp, like AD8620 with aural exciter. More slam than anything I've heard. It even makes the LM4562 sound dull, not to talk about OPA2107. Soundstage is at least on par with AD8620. But... it's very forward sounding and harsh.


Well, keep in mind that the AD8397 has 40000 times the Ib of the AD8620, so he'll need to make sure to balance bias currents or he'll be up to his ears in DC (literally?) :P
 
May 27, 2007 at 12:16 PM Post #26 of 27
Quote:

Originally Posted by slowpogo /img/forum/go_quote.gif
Does that hold true for all opamps in general?--that is, two single-channels adapted to a dual socket will give better performance than the same family dual-channel chip?


Well... cheap dual opamps have internally shared components, this means more stereo crosstalk (I also meant crosstalk and not crossover in my last post), because if there's load on one channel, it then somehow influences the other channel.
better opamps may have strictly separated left/right components, but then there is still the problem of electromagnetic emissions influencing the other channel. noise may be higher, because there isn't just the electromagnetic noise generated by one opa circuit, but from two chips.
and opamps are quite closely packed, so even spacing them just a millimeter apart means that the circuits are several times further apart.
and last but not least, there must be a reason that high end opamps only come in single packages. like the opa637/opa627, called by many the best opamp in existance. or for example the ultra-low-noise ad797. I don't think it would sport the same impressive low noise characteristics if it were a dual opamp.

Ok, short answer to your question: Yes.
edit: BUT.... the difference may be very minimal, especially if the surrounding circuit is noisy too. conclusion: don't toss your dual ad8610 away, but don't go changing all your dual opamp to two single opamps either. it will start making sense if you build a dual mono amp, meaning two completely separate amps, one for left and one for right
 
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